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<br />5.1 <br /> <br />V. REVISED FLOOD-HAZARD CONDITIONS ON HIE CORNET CREEK ALLUVIAL FAN <br />5_ I ,General <br />Employing the original grid system and dat.a base for the Cornet. Creek <br />alluvial fan described in the draft study report, the outflow discharges from <br />the detailed study of the fan apex were rout.l,d over the entire Cornet Creek <br />alluvial fan. The analysis procedure was identical to that. previously described <br />in t.he draft study report except. that bot.h grid elements numbers 1 and B4 were <br />used as inflow points, depending on the direction of flow on the east or west <br />side of the fan as determi ned from the detailed study of the fan apex. <br />Simulations were conducted only for the A~luvial Fan Flooding scenario, <br />as described in the draft study report, on the Cornet Creek alluvial fan. This <br />implies that the existing Cornet Creek channel is nonfunctiona,l (obstructed) <br />over t.he entire alluvial fan downstream of the fan apex. No additioral <br />invest. i gat i on of the Channel Flood i ng scenari 0 WilS made since the Puy'pose of th is <br />supplemental study was to identify the flood.h,lzard conditions over the fan <br />considering the influence of the fan apex. <br /> <br />5.2 H~ydraulic Results <br />Maximum flood depths and velocities fOY' the 100-year return fwriod wa.ter <br />flood and mud flow over the entire Cornet Creek alluvial fan were defined for <br />the with-berm, unobstructed channel and without-berm, obstructed channel flood <br />conditions on the alluvial fan apex. In the following sections the results for <br />each scenario are summarized. <br /> <br />5.2.1 Water Flood <br />5.2.1.1 With-Berm Flood Scenario <br />Hydraul ic model ing resul ts for the Cornet CI^eek all uvi al fan fo'r the water <br />flood, with-berm flood scenario are presented on Figures 5.1 and 5.2. Figure <br />5.1 delineates the maximum flow depths on the fan. Figure 5.2 illustrates the <br />expected maximum flow velocities on the fan. In general, the water flood is seen <br />to inundate the majority of the fan. The maximum depth over the fan was <br />predicted to be less than 1.5 feet. Over most of the fan, flow depths are <br />predicted to be less than 0.5 feet. Maximum velocities of flow over the fan <br />range between 1 and 8 fps. The highest velocities are predicted to occur on the <br />western half of the fan near the apex. <br />